Pulp stock consistency regulator



Sept. 15, 1970 B. COWAN PULP STOCK CONSISTENCY REGULATOR 2 Sheets-Sheet1 Filed April 19. 1968 1T7. 5A lrvvsnron B. Cow/m im zy g;

Arron/ways B. COWAN 3,528,281

PULP STOCK CONSISTENCY REGULATOR Sept. 15, 1970 Filed April 19, 1968 2Sheets-Sheet 2 TIq,EI

DIFFERENTIAL PRESSURE RECORDER CONTROLLER FRICTION AUTOMATIC TUBE 36DIAPHRAGM TYPE PRESSURE cans l j) 54 a REGULATED PULP ,4 Z CONSISTENCYREGULATOR uunsaumrzn 1 I '1 PULP sysnsm .INVENTOR B. COwAN United StatesPatent O" 3,528,281 PULP STOCK CONSISTENCY REGULATOR Ben Cowan, 5460Patricia Ave., Montreal 29, Quebec, Canada Filed Apr. 19, 1968, Ser. No.730,673 Int. Cl. G01n 11/04 U.S. CI. 73-61 14 Claims ABSTRACT OF THEDISCLOSURE A stock consistency regulator consisting of a housinginserted in the stock feed line, the housing having a stock samplingpipe located vertically therein and having an opening throughout itslength on the downstream side, a pump drawing the stock from the stocksampling pipe and passing it through a friction tube terminating in adiffuser and a nozzle in a discharge box, an outlet from the dischargebox leading back into the housing downstream of the sampling pipe. Apair of diaphragm type pressure cells are located in the discharge boxopposite the discharge end of the nozzle and the other located in thewall of the housing downstream of the sampling pipe, and a differentialpressure controller connected to said diaphragm pressure cells andactuating a control valve to regulate the feed water into the stockupstream of the housing.

The present invention relates to a method and apparatus for measuringand regulating the consistency of a flowing fluid medium. Particularly,the invention relates to an automatic consistency regulator to maintaina constant consistency, i.e., constant ratio of solids to water byweight, in a flowing solids/fluid stream.

The apparatus of the invention has particular application to the papermaking industry to provide the desired solid-liquid consistency to thepaper making stock.

In the making of paper, water is added to ground wood pulp, sulphitepulp or whatever other material from which the paper is to be made andthese materials thoroughly mixed in a mixer or pump and from theretransferred to the stock storage boxes and the Fourdrinier end of apaper machine. It is essential that the stock be of a proper andconstant consistency since measurements of the quantity of pulpthroughout the system is based on volume of flow.

Many attempts have been made to provide apparatus for determining andregulating the consistency of the pulp stock. These usually involve theprinciple of changes in friction or shear value with changes inconsistency of the stock, with a more liquid consistency stock offeringless friction resistance to flow. The changes in friction or shear valueof the stock flow are measured and used to control a water dilutionvalve which regulates the ratio of water to pulp solids.

One of the conventional consistency regulators consists of a spinningdisc or paddle positioned in the pulp stock and driven by an electricmotor at a constant speed, with the current flow necessary to drive themotor at the constant speed being used as a measure of the friction orconsistency of the stock.

Another type of regulator consists of positioning a probe in a flowingstream of pulp, with the friction on the probe being a measure of theconsistency of the stock.

These two types of regulators are the units normally in use, as they canbe mounted directly in a pipe line and close to the source pump. Onedisadvantage however is that pipe line units having a driven disc orpaddle must be fitted with a stuffing box where the drive shaft passesthrough the pipe wall. The frictional load at this point is much greaterthan the fluid friction, and any changes in stuffing box characteristicswill upset the consistency regulation and require recalibration.Moreover, it is gen- 3,528,281 Patented Sept. 15,, 1970 erally necessaryto provide sealing water to the stufling box and this water must beregulated in pressure to correspond with the pipe line pressure. Thelatter will vary and cause sealing difficulties. Another disadvantage isthat the measuring unit is located at one point, and this can result inmisleading effects if there is Stratification in the pipe line.

In the case of probes depending on velocity of flow to develop friction,the unit is accurate only in a limited range of velocities and theresults are inaccurate if velocity of flow varies widely.

Another type of conventional regulator used and which is possibly themost accurate, involves extracting a sample of pulp from the stock flowand permitting it to flow through a passage under a gravity head, thefriction and consistency being measured by the head required to maintaina constant flow. Such apparatus however has the defect that a sampleonly is measured which may be misleading if there is stratification offlow at the source. Moreover a portion of the system is open andrequires showers and regular cleaning to avoid pulp build-up. Also theregulator must be located to suit the sampling arrangement and canrarely be located close to the pumping unit. This causes a slow responseto changes of consistency in the system. In addition such aninstallation is complicated due to sampling lines, water lines,overflows, etc.

The consistency regulator of the present invention provides all of theadvantages of sampling type regulators and avoids the disadvantagesinherent in such types.

The apparatus of the invention consists of a section of pipe which ispositioned directly in and forms part of the stock flow pipe line. Thepipe section is provided with a central or sampling tube positionedtherein and normal to the axes of the pipe and stock flow, and having aslotted opening on the downstream side. One end of the sampling tube isopen through the wall of the pipe section and is provided with a pump todraw a fixed volume of stock sample through the slotted opening and outthe open end of the sampling tube. The slotted opening in the samplingtube extends the full length of the tube and completely across theinterior diameter or width of the pipe thereby avoiding Stratificationand turbulence complications when sampling. Moreover as the slottedopening is on the downstream side of the sampling tube the velocity ofthe stock flow through the pipe line does not affect the sample flow tothe pump.

The pump which may be a straight bladed impeller is driven by anelectric motor, and the speed of the impeller is designed to generate aconstant hydraulic head. The flow through the friction tube is afunction of the hydraulic head which is constant, and the friction whichvaries with consistency. Thus it can be calculated that, if theconsistency varies from 3 to 3 /z% the flow through the tube will varyfrom 200 U.S. g.p.m. to U.S. g.p.m. Measurement of the flow rate willthus give a measurement of consistency. This can be measured by amagnetic flow meter, venturimeter orifice, or impact plate.

Method A.--The end of the friction tube, remote from the pump, projectsinto a discharge box and the jet from the discharge pipe nozzle isdirected against a diaphragm pressure measuring element protected by aflexible rubber cover. This measuring element measures the staticpressure of the system plus the impact pressure from the nozzle. Asecond diaphragm pressure measuring element is mounted on the pipe lineto measure the static pressure in the system only. The two pressuremeasuring elements are connected to a differential pressure cell, whichproduces a net measurement of impact pressure from the nozzle which isconnected in turn to a controller actuating the addition of dilutionwater to control the consistency of the pulp stock.

Method B.In this case the friction tube discharges freely into thedischarge box. The return opening between the discharge box and the mainstock pipe is fitted with an orifice. The two pressure measuring cellsare connected as before, one on the discharge box and the second on themain stock pipe and measure the volume of flow (and consistency) by thepressure drop across the orifice.

The length of the friction tube can be varied and the tube can be coiledto suit the particular installation, types of stock to be measured or tovary the sensitivity of the unit.

The present apparatus utilizes the most accurate principle of the opensampling consistency regulator but is, in fact, a closed type regulatormounted directly in a pipe line. Moreover, it measures friction lossdirectly, with a controlled flow, and gland friction has no effect onthe measurement. It is thus more accurate than other pipe line types ofregulator.

The unit of the invention can be installed in any position, horizontalor vertical, and at any point in the pipe line, as near the source pumpas desired, and it cannot be damaged by solids passing through the pipe.The unit requires no sealing water at controlled pressures, and hassimple mechanical parts for easy maintenance.

It is the principle object of the present invention to provide apparatusfor automatically measuring the consistency of a fluid medium flowingthrough a pipe line, and which measurements are not affected by changesin velocity of the fluid flow or by stratification or turbulence in thepipe line.

It is a further object to provide a regulator for accurately andautomatically regulating the consistency of a flowing fluid medium in apipe line, which can be installed in any horizontal or vertical positionat any point in the pipe line and which is constructed of simplemechanical and electrical components for ease of maintenance andreplacement.

It is another object to provide apparatus for measuring the consistencyof a solids/liquid material flowing in a pipe line, comprising a pipesection positioned in and forming part of the pipe line, and a samplingtube positioned within and extending completely across the pipe sectionand normal to the axis thereof, and a slot in the sampling tube on thedownstream side thereof, and an opening through the pipe section at oneend of the sampling tube, and a casing positioned adjacent the openingand exterior of the pipe section and a friction tube having a first endconnected to the casing and a second end connected to the pipe sectiondown-stream of the sampling tube, and a pump impeller rotatably mountedin the casing and means to rotate the impeller to draw a sampling streamof the material through the opening and force a variable volume of flowthrough the friction tube, and pressure sensing means are provided tomeasure the variation in flow.

It is still another object to provide a method of measureing theconsistency of a solids/liquid flow in a pipe line comprisingwithdrawing a sample stream representative of the material flow acrossthe pipe line from the pipe line and forcing the sample stream through afriction tube having ingress and egress ends, and measuring the pressureof the sampling stream at the egress end of the friction tube, as ameasurement of the consistency of the material.

These and other objects will become apparent from the followingdescription and accompanying drawings where- FIG. 1 is a side elevationpartially in section of the sampling and measuring apparatus of theinvention;

FIG. 2 is a plan sectional view taken along line 22 of FIG. 1;

FIG. 3 is a plan view partially in section taken along line 3-3 of FIG.1;

FIG. 3A is a fragmentary view showing a portion of FIG. 3 in a slightlymodified embodiment of the invention;

FIG. 4 is a vertical sectional view of the discharge box shown in FIGS.1 and 3 showing Method A.

FIG. 5 is a transverse section of the discharge pipe within the pressurebox taken on the line 5-5 of FIG. 4.

FIG. 6 is a vertical sectional view of the discharge box but showingMethod B.

FIG. 7 is a control diagram showing the stock flow and sampling flow andregulation of the stock consistency.

Referring now particularly to the drawings numeral 2 represents a pipesection which forms part of the apparatus of the invention and which ispositioned in and forms a section of the paper stock pipe line. The pipesection 2 may be placed at any desired point along the stock pipe line,and as close to the source pump as desired.

In the drawings the pipe section 2 is shown as being generallyrectangular in cross-section, but it can equally be round or of otherconfiguration. Positioned centrally within the pipe section 2. is asampling tube 4 which extends completely across the interior of the pipesection 2, and is provided with a slot or opening 6 on the downstreamside. See particularly FIG. 2. The sampling tube 4 which is used towithdraw, by means elaborated below, a sample stream flow from the mainpipe line. The sampling tube is preferably positioned vertically and asthe slot 6 extends the complete length of the tube 4 the samplewithdrawn is representative of material flow vertically across the pipethereby avoiding incorrect consistency measurements due tostratification or turbulence of the material in the pipe. Also as thesample stream is withdrawn on the downstream side of the sampling tubethe passage of damaging solids through the regulator is avoided, and thesampling stream is unaffected by velocity change in the main pipe flow.

In the drawings arrows 8 indicate the direction of flow of the paperstock through the pipe line, and arrows 10 the direction of flow of thesampling portion.

It will be noted that the central section 12 of the pipe section 2broadens adjacent the sampling tube 4 in order to maintain the normalcross section of the pipe line so that the presence of tube 4 does notaffect the flow of paper stock therepast.

One end of the sampling tube 4 opens at 14 through the pipe section 2into a pump chamber 16 formed by pump casing 18. Positioned in the pumpchamber 16 adjacent the opening 14 is a pump impeller 20 which issupported by shaft 22. mounted on bearings at 24 and sealed at 26. Thepump impeller blades are rotated by an electric motor 28 through belts30 and sheaves or pulleys 32. This latter equipment is mounted on frame33 The casing 18 opens at 34 into a first or ingress end of a frictiontube 36 which empties at a second or egress end 38 back into the mainpaper stock flow downstream of the sampling tube 4. In the drawings thefriction tube 36 is shown as being generally curved and coiled and withbends and straight sections but it can be of any configuration, and ofany length to suit the types of stock to be measured or to vary thesensitivity of the unit.

As discussed above the slotted sampling tube 4 extends completely acrossthe main pipe line thus enabling the sampling stream to berepresentative of the complete material flow through the pipe lineirrespective of any stratification that may be present. Moreover thepresence of the sampling tube will act to de-stratify any stratificationin the main pipe flow and the return of the blended sampling stream at38 will further act to blend the material in the main pipe line.

The speed of the impeller pump 20 is designed to generate a hydraulichead sufficient to force a variable volume of sampling stock flowthrough the friction tube 36 which is coiled or curved or otherwisedesigned to provide suflicient friction to dissipate the hydraulic headgenerated by the pump.

The friction tube 36 discharges into a discharge box 38 through a nozzle40, see FIGS. 4 and 5. This nozzle 40 consists of a diffuser section 42having diffuser plates 44, and an adjustable nozzle tube 46 secured inits axially adjusted position by the screw 48.

The wall 50 of the box 38 has an aperture 52 axially in alignment withthe nozzle 40 and a diaphragm pressure measuring element 54 is securedto the outer surface of the wall 50 over the aperture 52. The measuringelement 54 is protected by a flexible rubber cover 56 mounted on theinner surface of the wall 50.

The bottom wall 58 of the box 38 has a discharge opening 60 and a shortlength of pipe 62 connects the box 38 with the downstream end 64 of thepipe 2.

A second diaphragm pressure measuring element 66 is located in the pipe2 at a position preferably down stream from the sampling tube 4 as seenin FIGS. 1 and 2. A suitable cover plate 38a permits ready access to thepressure chamber for maintenance purposes.

FIG. 3A shows a slightly modified embodiment wherein a venturi meter 90is provided in the friction tube 36, upstream from the discharge box 38.Such a venturi meter may also be used in the further modified embodimentof FIG. 6, hereinafter described.

In an alternative arrangement shown particularly in FIG. 6 the frictiontube 36 terminates in an opening in the wall 68 of the pressure box 38.A diaphragm pressure measuring element 54a is mounted on the wall 50 asabove described and illustrated in FIG. 4 and is located preferablydirectly opposite from the discharge of the pipe 36 into the box.However, in this case the element 54a could be mounted on any wall ofthe box and give satisfactory pressure indication.

The discharge opening 60 from the box is partially blocked by an orificeplate 70 having an orifice 72 controlling the discharge outflow from thebox 38 to the downstream end 64 of the pipe 2.

In the arrangement shown in FIG. 4 the flow velocity is measured byimpact and in the alternative arrangement shown in FIG. 6 measurement offlow velocity is by the pressure drop across the orifice 72.

By comparing the differential pressure between the two diaphragms ameasurement of the consistency of the sample flow and hence the mainstock flow can be determined and the necessary regulation made to eitherincrease or decrease the liquid content of the paper stock as theoccasion demands to obtain the desired consistency.

This may be better understood by reference to the accompanying FIG. 7which is a flow and control diagram. In this figure consistencyunregulated pulp is forced through pipe 72 'where at point 74 liquid(water) is introduced via water pipe 76 to give the pulp stock thedesired consistency. The stock and water are thoroughly mixed andblended at mixer and pump 78 and forced through pipe 80 to the system.

The consistency regulator of the invention shown generally at 82 in FIG.7, is positioned in pipe line 80 and sampling is taken and measured infriction tube 36 as discussed above. The pressure differential measuredby the first and second pressure diaphragms 54 and 66 is recorded by thedifferential pressure recorder controller 82 which controls theautomatic water control valve 84 to increase or decrease the watersupply to stock pipe 72 to maintain the consistency of the stock mixtureflowing in pipe 80 at a desired and constant level.

In the operation of this invention, the head generated by the impeller20 will be constant, and the friction loss through the tube will varywith the consistency of the stock. Using published friction factors forpulp stock flowing in pipe lines, the following table shows the measureof variation of flow with consistency.

TABLE 1 Thus the measure of velocity in the tube 36 or velocity head canbe used to control the consistency of the pulp stock to a set point.

The velocity may be measured in the manner above described or by the useof a venturi meter, magnetic flow meter, etc.

The above described apparatus ensures that, so long as the impeller pump20 is in operation a continuous sampling of the pulp stock flow iswithdrawn, its consistency sensed, and a controlled feed of water to thepulp stock is made automatically so that the pulp stock downstream ofthe regulator is of uniform consistency. Furthermore, as the sample ofpulp stock withdrawn from the main pipe line is taken from across thefull depth of the'pipe and is mixed in the pump 20 before the pressuredifferential is recorded, the accuracy of the pressure differentialrecording is much greater and hence the control of the water feed intothe pipe 72 will ensure that the consistency of the pulp will be asdesired. This being so, once the system is in operation, only minorregulation will be required and this will be accomplished automatically.

What I claim is:

1. Apparatus for measuring the consistency of a solid/ liquid materialflowing in a pipe line, comprising a pipe section positioned in andforming part of the pipe line, a sampling tube positioned Within andextending completely across the pipe section and normal to the axisthereof, the said sampling tube having a slot on the downstream sidethereof, an opening through the pipe section at one end of the samplingtube, and a casing positioned adjacent the opening and exterior of thepipe section, a friction tube having a first end connected to the casingand a second end connected to the pipe section downstream of thesampling tube, a pump impeller rotatably mounted in the casing, means torotate the impeller to draw a sampling stream of the material throughthe opening and force a variable volume of flow through the frictiontube, and sensing means to determine the variation in flow withconsistency.

2. Apparatus according to claim 1 in which the downstream end of thefriction tube terminates in a chamber and a discharge opening connectsthe said chamber with the pipe section downstream from the samplingtube.

3. Apparatus according to claim 2 in which said sensing means comprise apressure responsive venturi meter provided in said friction tube.

4. Apparatus according to claim 2 in which the said sensing meansconsists of two elements, one sensing the pressure in said chamber andthe other sensing the pressure in the said pipe section.

5. Apparatus according to claim 4 furthercomprising means for comparingthe pressure differential between the first and second of said sensingelements as a measurement of the consistency of the liquid materialflowing in the pipe line.

6. Apparatus according to claim 4 further comprising a differentialpressure controller and a water control valve controlled by saiddifferential pressure controller to increase or decrease water supply tothe material in the pipe line upstream of the sampling tube to maintaina selected material consistency.

7. Apparatus according to claim 6 comprising the further step ofutilizing the pressure differential measurement to control water inputinto the solids/fluid flow.

8. Apparatus according to claim 2 in which the said friction tubeterminates in a nozzle within the said chamber and one pressure sensingmeans is of the diaphragm impact type and is located in a wall of thesaid chamber axially opposite from the discharge end of said nozzle.

9. Apparatus according to claim 8 wherein the opening through the pipesection is at the upper end of the Sampling tube.

10. Apparatus according to claim 1 in which the downstream end of thefriction tube terminates in a chamber and a discharge opening connectsthe chamber with the pipe section downstream from the sampling tube, thesaid discharge opening including a restricted orifice and the saidpressure sensing means consists of two elements, one sensing thepressure in said chamber and the other sensing the pressure in the saidpipe section.

11. Apparatus according to claim 1 wherein the friction tube isgenerally coiled or curved consisting of bends and straight sections.

12. Apparatus according to claim 1 wherein the sampling tube ispositioned vertically within the pipe section, and the slot in thesampling tube extends the full length thereof.

13. Apparatus according to claim 1 wherein the pipe section broadens inthe area of the sampling tube.

14. In a system for measuring and regulating the consistency ofsolids/liquid material flowing in a pipe line having a water controlvalve for controlling the amount of water added to the material to alterits consistency, comprising a pipe section positioned in and formingpart of the pipe line, and a sampling tube positioned within andextending completely across the pipe section and normal to the axisthereof, and a slot in the sampling tube on the downstream side thereof,and an opening through the pipe section at one end of the sampling tube,and a casing positioned adjacent the opening and exterior of the pipesection and a friction tube having a first end connected to the casingand a second end connected to a pressure chamber, the said pressurechamber having an opening connected to the pipe section downstream ofthe sampling tube, and a pump impeller rotatably mounted in the casingand means to rotate the impeller to draw a sampling stream of thematerial through the opening and force a variable volume of flow throughthe friction tube, and pressure sensing means located at said pressurechamber and said pipe section downstream from said sampling tube toobtain a measurement of the consistenccy of the material, and means toregulate the water control valve to regulate the consistency of thematerial flow.

References Cited UNITED STATES PATENTS 3,017,767 1/1962 Mossberg 73-543,027,756 4/1962 Head 73-54 X 3,057,187 10/19,62 Read et al. 73-613,163,172 12/1964 Buzzard 73-54 X S. CLEMENT SWISHER, Primary ExaminerJ. W. ROSKOS, Assistant Examiner US. Cl. X.R.

